1. Field of the Invention
This invention relates generally to the duplication of magnetically recorded information. More specifically, the invention relates to a magnetic head for inductively recording on a master medium, or playing back information from a slave medium, in the form of a rotatable drum.
2. Description Relative to the Prior Art
The duplication of magnetically recorded information can be accomplished by simply feeding an electrical playback signal from a master recorder to multiple slave recorders connected in parallel, where the information is duplicated in real time by each of the slave recorders.
Duplication of magnetically recorded information can also be accomplished by a contact printing method, using either an anhysteretic, hysteretic or a thermal technique. In this method, a master medium, having information recorded thereon, is placed in contact with a slave medium under conditions that promote efficient transfer of recorded information without causing demagnetization of the master medium. For example, contact transfer is usually performed by transferring magnetic information from a high coercivity master medium to a lower coercivity slave medium while the master and slave media are held in non-slipping engagement with each other.
Among other things, contact transfer offers an apparent advantage over "real time" duplication in that the recording of information on the slave medium is accomplished without the slave medium coming into frictional contact with a magnetic record head. This, of course, obviates wear and tear of both the slave medium and magnetic head. This is particularly important in a situation involving the recording of short wavelength signals wherein it otherwise would be imperative that intimate contact be maintained at a media-to-head interface to minimize spacing losses.
Contact transfer offers a further advantage when repetitive information is to be duplicated. This is because the master magnetic medium can be in the form of a compact roller or rotatable drum, with the information to be duplicated recorded on a magnetizable material on the circumferential surface of the drum. In this situation, the drum is rotated with its peripheral speed equal to the translational speed of a slave magnetic tape which is held in contact with the circumferential surface of the drum. Information magnetically recorded on the circumferential surface of the drum is transferred repetitively to the slave tape at a rate corresponding to the rotational speed of the roller. U.S. Pat. No. 3,277,244 discloses a system in which magnetically recorded information is transferred between a magnetic tape and a rotatable drum, by means of an anhysteretic contact printing method.
Whether the drum (or roller) functions as the master medium or as the slave, a magnetic head commonly serves as the means by which information is either initially inductively recorded on or is initially inductively played back from the drum. In either case, the transducing gap of the head should be placed in intimate contact with the cylindrical surface of the drum to enhance the signal-to-noise ratio of the signal recorded on, or played back from, the drum. When there is intimate contact between the drum and head, however, a magnetic head having a media-contact surface of conventional design is susceptible to an angular displacement in its position, under the influence of rotational movement of the drum. Even though the head and the rotational surface of the drum may remain in physical contact, a small rotation of the head would move its transducing gap away from the surface of revolution of the drum, and thereby dramatically reduce recording/playback performance.